What does a lancelet use its pharynx for?

What does a lancelet use its pharynx for?

Like most tunicates, lancelets are filter feeders with the pharynx situated in an atrial cavity where it functions to filter food particles from the water currents that flow through the cavity. Water is taken in through the mouth and expelled through an opening called the atriopore.

What is notochord function?

The notochord is the defining structure of the chordates, and has essential roles in vertebrate development. It serves as a source of midline signals that pattern surrounding tissues and as a major skeletal element of the developing embryo.

What is the function of buccal Cirri?

Function. Buccal cirri function as a food processing organ that is used to prevent larger particles from entering the oral hood. The buccal cirri does this by working with the velar tentacles to create a comb like feeding appendage that sifts the particles that are entering via the water stream.

How do Branchiostoma feed?

Branchiostoma is a typical ciliary feeder. It feeds on planktonic micro- organism brought along with a respiratory cum food water current which constantly enters the mouth and leaves through atriopore. Digestive system consists of an alimentary canal and digestive glands.

Why Branchiostoma is called lancelet?

Although the name Amphioxus is commonly used, Branchiostoma is the correct scientific name for this genus, so I’ll use that name on this page. This organism also goes by the common name “lancelet,” supposedly because it resembles a small lance.

Is Branchiostoma a vertebrate?

2 Mechanoreceptors in lancelets. The lancelets (often known as amphioxus and placed in a group known as cephalochordates, of which the best known are in the genus Branchiostoma) are small marine chordates that are most closely related to the vertebrates.

What happens to the notochord in vertebrates?

Vertebrates convert the notochord into the cushioning intervertebral discs, which protect the vertebrae from smashing together. By the time a human is around 4 years old, however, the original notochord has been entirely replaced in the spine with other materials.

What happens if the notochord is dysfunctional?

When the cells of the notochord are damaged, the chordacentra cannot form properly (Fleming et al., 2004). However, when the formation of somites is disrupted, the vertebrae remain normally patterned (see Fleming et al., 2015 for a review).

What is wheel organ in Branchiostoma?

The wheel organ is a specialized epithelium in the roof and sides of the adult lancelet oral cavity. It borders the oral epithelium proper, separated by a thin strip of margin cells which are not ciliated but contain a few large dense-cored vesicles apically.

What is velum Branchiostoma?

The posterior wall of the vestibule is the velum, a vertical, muscular, transverse partition covered by larger buccal cirri. The cirri play a role in selecting or rejecting food items by the filter feeding ammocoetes. They are both mechanical and sensory. The large mouth is an opening in the center of the velum.

What is filter feeding in Branchiostoma?

Branchiostoma feeds on protozoans, algae, diatoms and other organic particles. A) It filters its food from water with the help of wheel organ. Hence, it is a filter feeder.

What is absent in Branchiostoma?

So, the correct answer is ‘Head’.

What is the respiratory role of the pharynx in Branchiostoma?

Since the blood of Branchiostoma lacks any respiratory pigment and also occurs in lymph-spaces in the fins and meta-pleural folds, it is doubtful whether the pharynx has any role in oxygenation. Many workers are doubtful about the respiratory role of pharynx and lay more emphasis on its role in food con­centration.

What is the mode of feeding of Branchiostoma?

Branchiostoma feeds on micro-organisms brought into the pharyngeal cavity together with the respiratory water current. It exhibits a typical instance of ciliary mode of feeding. 3. External Structures of Branchiostoma:

What is the external structure of Branchiostoma?

External Structures of Branchiostoma: Branchiostoma is a small lancet-shaped creature with sharply pointed anterior and posterior ends (Fig. 3.12B). The length of the animal varies from 5-8 cm. The body is elongated and flattened from side to side. The body is distinguishable into the body proper and definite postanal tail.

What is the function of the buccal cirri in a Branchiostoma?

Branchiostoma is a microphagous animal. The food or ‘sea soup’ consists of protozoans, algae, diatoms and other organic particles. Branchiostoma obtains food by filtering the stream of waters that enters the pharyngeal cavity. The wheel organ produces a vortex. The buccal cirri become curved to form a sieve to prevent the entry of large parti­cles.